We therefore examined LAM tissue for the presence of wild type, non-LAM cells by a range of methods, and we show that LAM nodules contain wild type fibroblast-like cells which are attracted to LAM cells, in part by production of the chemokine CXCL12, and that LAM cell/fibroblast aggregates protect LAM cells from stress-induced apoptosis. The gene discussed is CXCL12; the disease is lymphangioleiomyomatosis.